Abscisic acid metabolism

Chapter 8. Abscisic acid metabolism and its regulation Jan A.D. Zeevaart. 

Seo, M. Hanada, A. Kuwahara, A. Endo, A. Okamoto, M. Yamauchi, Y. North, H. Marion-Poll, A. Sun, T.P. Koshiba, T. Kamiya, Y. Yamaguchi, S. Nambara, E. (2006). Regulation of hormone metabolism in Arabidopsis seeds phytochrome regulation of abscisic acid metabolism and abscisic acid regulation of gibberellin metabolism. Plant Journal, Vol.48, No.3, (November 2006), pp. 354-366, ISSN 0960-7412... 

Hartung, W., Gimmler, H. Heilmann, B. (1982). The compartmentation of abscisic acid, of ABA - biosynthesis, ABA - metabolism and ABA conjugation. In Plant Growth Substances 1982, ed. P.F. Wareing, pp. 325-334. London Academic Press. 

Walton, D.C., Harrison, M.A. Cote, P. (1976). The effects of water stress on abscisic acid levels and metabolism in roots of Phaseolus vulgaris and other plants. Planta, 131, 141. ... 

Phytohormones such as ethylene, salicylic acid (SA), JA, and abscisic acid (ABA) regulate responses of plants to stresses via action referred as signaling crosstalk. Moreover, reactive oxygen species (ROS), the toxic byproducts of aerobic metabolism, play the important role of signaling molecules. Usually, the defensive responses of plants depend on the interaction (positive or negative) between phytohormone signaling pathways rather than on the independent contribution of each of them. " ... 

Chu, C., Dai, Z., Ku, M.S.B. Edwards, G.E. (1990). Induction of crassulacean acid metabolism in the facultative halophyte Mesem-bryanthemum crystallinum by abscisic acid. Plant Physiology 93, 1253-60. 

Figure 4. Metabolic pathway of abscisic acid (ABA) via the unstable intermediate 6 -hydroxymethyl-ABA to PA and DP A...

The uptake of radioactive abscisic acid by radish leaf discs has been described87 and its metabolism (to unidentified compounds) by root segments of Phaseolus coccineus88 and by pea seedlings during and after water stress has been reported.89... 

Flores, S., and Smart, C.C., 2000, Abscisic acid-induced changes in inositol metabolism in Spirodelapolyrrhiza. Planta 211 823-832. 

Further studies of abscisic acid (53) biosynthesis showed that the epoxyacid (52) was incorporated into tomatoes whereas the all-trans-isomer was not. In beans, [2- C]abscisic acid is rapidly (15 min) metabolized and the products are neither a glucoside nor a b-hydroxy-derivative. " ... 

Metabolite C , derived from metabolism of (+)-abscisic acid by tomato shoots, has been assigned structure (27) and on methylation rearranged to the methyl... 

Metabolite C was first recognised by metabolic studies using [2- C]abscisic acid synthesised in the normal way from [2- C]bromoacetic ester. t-Butyl chromate oxidation of a-ionone provides an efficient synthesis of abscisic acid (Scheme 3). A large number of compounds related to abscisic acid have been synthesised to check their biological activity. In general, conventional synthetic methods were used. The Reformatsky reaction may be used as an alternative to the Wittig reaction for the synthesis of a-ionylidene acetic ester. 

These variations in behavior indicate that harvesting melons at different stages of maturity causes subsequent biochemical events involved in amino acid accumulation to follow markedly different pathways. Recent work shows that melon fhiit harvested up to ten days before commercial maturity exhibits climacteric behavior with respect to ethylene production showing that at least this aspect of ripening is not completely inhibited by premature separation from the plant(P). However, the amount of ethylene produced is dependent on maturity at harvest and fruit harvested five days prematurely generated only about half of the amount of ethylene produced by fruit harvested two days before maturity. Also the lag time required to initiate ethylene production after harvest depended on maturity and was longer for prematurely harvested fruit. Changes in the content of the phytohormone abscisic acid were also correlated with that of ethylene. However whether the different maturity related metabolic responses observed above result from the action of these or other plant hormones awaits further study. 

Abscisic acid (ABA) is a 15-carbon acid, related in structure to one end of a carotene molecule [83], Four stereoisomers exist, differing in the orientation of the carboxyl group and the sidechain attachment to the ring. The natural ABA is the c/y-(+)-isomer shown in Fig. le. It is made from zeaxanthin via xanthoxin, probably in plastids (see Chapter 8). ABA can be made in all parts of a plant, with the leaves and the root cap being sites of extensive synthesis. It can be metabolized into phaseic acid, which is active in some, but not all ABA-sensitive processes [83]. 

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